As the use of breast reconstruction and postmastectomy radiotherapy (PMRT) has increased over the past decade, the typical approach to integrating radiotherapy with breast reconstruction has provoked intense controversy in the management of breast cancer. PMRT can lead to an increased frequency of complications in the reconstructed breast. Conversely, the reconstructed breast can increase the complexity of radiotherapy delivery. How to minimise the frequency of complications without compromising oncological or cosmetic outcomes of the reconstructed breast is an important shared multidisciplinary goal for oncologists and their patients. Several questions remain, however, regarding the type of reconstruction that should be used with PMRT, when reconstruction should be done relative to PMRT and whether radiotherapy treatment should be directed towards the tissue expander or the implant for women who opt for a two-stage expander–implant reconstruction. Following advances in the planning of radiotherapy treatment, new questions about the application of these technologies in the setting of breast reconstruction have arisen. In this Review, we address these questions by reviewing contemporary evidence on the optimal integration of radiotherapy and breast reconstruction in the management of breast cancer.